The primary objective of this proposal is to investigate the cardiovascular and sleep effects of the stimulant medications commonly used in children diagnosed with attention deficit hyperactivity disorder (ADHD). We propose 2 specific aims to test the hypotheses that stimulant medications in children with ADHD: 1) circadian blood pressure patterns and raise blood pressure, and 2) affect overall level of hyperactivity and quality of sleep. Using a double blind, placebo-controlled, random crossover design, 100 children aged 5 to 15; with ADHD by DSM-IV criteria will undergo 24-hour ambulatory blood pressure monitoring (ABPM) and actigraphy while receiving their usual dosing regimen of stimulant medication and while receiving placebo. Each subject will receive their usual stimulant medication (either methylphenidate or amphetamine-salt) for three and an identical placebo for three days in random order. At the end of the 1st 3-day period, subjects undergo 24-hour ABPM and then crossover to the other arm of the study. After the 2nd 3-day period, subjects will again undergo 24-hour ABPM. The issue of cardiovascular and other side effects has become increasing important since ADHD is a highly prevalent disorder and prescriptions for psychotropic medications in children with behavioral disorders such as ADHD have risen significantly over the last 5 years. Virtually all studies stimulant medications have found significant dose response elevations in some combination of systolic, diastolic, and mean blood pressure. Chronic blood pressure elevation is one of the leading causes of attacks, stroke and renal failure. Since many children are treated for years with these medications, serious cardiovascular consequences of their chronic usage may result. The studies proposed will provide the published data on the effect of both short and long-acting stimulant medications on 24-hour blood pressure patterns and the likelihood of inducing sustained hypertension. In so doing, these studies may suggest that long term use of these drugs places children at high risk for cardiovascular disease that may ultimately result in significant morbidity and mortality in adulthood. If so, physicians who prescribe these medications must increased awareness of the need to monitor blood pressure carefully in these children.